That Extraneous Floating Tissue

That Extraneous Floating Tissue

Extraneous tissue, commonly known as floaters, in the lab, will never be completely eradicated from our testing practices, but we can take steps to understand where it comes from, and how we can prevent it.

Main sources of floaters include, the grossing bench, the embedding stations, and the microtomy stations. At each station, cleaning is an important factor in prevention of floaters. If forceps aren’t cleaned between each and every specimen, you can get fragments of tissue that carry from one specimen to the next. Similarly, if forceps are not cleaned between cassettes, tissue can get carried from one block to the next. Also be mindful of the wells the forceps are stored in and ensure regular cleaning of these occurs. At the microtomy station, ribbon fragments can get picked up if you’re not cleaning the water bath surface between blocks. Cleaning! Cleaning! Cleaning! It really is super important.

Make sure to use common sense practices in your lab, such as not putting your fingers in the water bath or touching the slide in parts other than the sides. Wearing gloves can also reduce the likelihood of your own cells becoming extraneous tissue.


Content provided by Fixation on Histology

Cleaning Embedding Molds

Cleaning Embedding Molds

A common method of cleaning embedding molds involves putting them in the processor during the clean cycle. Though this method is effective, and pervasive, it may be discouraged by management or your vendor reps, concerned about the potential effect on the processor. Its common to hear that this method of cleaning is hard on the processor and paraffin from the molds can get clogged in the lines of the processor. These can be valid concerns, so if you’re going to keep putting your molds in the processor, change cleaning reagents more frequently to prevent wax buildup.

If you’re looking for an alternative method of cleaning, soaking them in a bucket of xylene and rinsing in alcohol is common. Or, you can put the molds in a metal container with water and detergent, put it over a hot plate and let it boil. Once it is cooled any left-over paraffin will collect at the top. Let it harden and then peel it off. Rinse the molds and let them dry. This method might be easier for a small, low-volume lab though, and may not be efficient in a larger lab.

Some labs simply melt off the paraffin and then use gauze to wipe the molds clean, then wash in hot water with detergent. Or, avoid the problem altogether and switch to disposable molds.

First posted on NSH’s “Fixation on Histology” Blog.

Relevant Products:

Formaldehyde: OSHA Regulations

Formaldehyde: OSHA Regulations

OSHA stands for the Occupational Safety and Health Administration, a government organization created in 1970 as part of the Occupational Safety and Health Act. Its job is to ensure safe working conditions across all types of industries, including healthcare, making it another organization, on top of CLIA and CAP that has authority over safety regulations in your laboratory. For example, OSHA has a section on formaldehyde, which provides guidelines for proper training, PPE, and disposal of formaldehyde contaminated clothing.


Several of the OSHA formaldehyde regulations specify training requirements, such as only those who are properly trained may remove contaminated material for cleaning or disposal (1910.1048(h)(2)(III) and only people who are properly trained to recognize hazards of formaldehyde may enter regulated areas 1910.1048(e)(2).

These regulated areas are those defined in the previous sections as areas “where the concentration of airborne formaldehyde exceeds either the TWA or the STEL”. These regulated areas must have signs posted at entrances notifying that there is potential danger from formaldehyde, that it may cause cancer, skin, eye and respiratory irritation, and the area is available to authorized personnel only.

To be in compliance with OSHA your lab should have a training program for anyone exposed to formaldehyde at or above 0.1 ppm. Training must be completed when they are initially assigned to the area of formaldehyde exposure, whenever there are new conditions impacting the formaldehyde exposure, and at least once annually. OSHA also specifies what must be included in the training, which includes items such as, symptoms of formaldehyde exposure, how to limit exposure through safety, proper use of PPE (personal protective equipment), emergency clean up, and how to report symptoms to your employer.

Personal Protective Equipment (PPE)

PPE refers to personal protective equipment. PPE is essential for protecting your skin, as well as your clothing from formaldehyde contamination. OSHA requirements specify that PPE that has become contaminated must be cleaned or laundered before reuse, and this contaminated equipment or clothing, should NOT be taken home once contaminated. Any clothing that is contaminated is required to be treated as, and disposed of as, hazardous waste. If proper PPE is in place you shouldn’t be getting formaldehyde on your clothing. If you are finding contamination to be a regular problem, you will want to look at your lab’s policies for safety in general, as you may be violating other OSHA requirements for hazard communication, ​chemical hygiene, etc.

Additional Information

Click here to view a complete list of OSHA regulations for formaldehyde.

First published on NSH’s Blog.

Back to Top

Join The Club!

Be the first to learn about
our amazing products

let's save the world together

Enter your email address to subscribe to this blog and receive notifications of new posts by email.